1. Technical Field
The present invention relates to an electro-optical device including a liquid crystal device, a projection-type display device, and an electronic device, and more particularly to a peripheral configuration of pixel electrodes of the electro-optical device.
2. Related Art
The pixels with pixel electrodes are arranged in the matrix on an element substrate for use in the electro-optical device, such as a liquid crystal device and an organic electroluminescence device, and the pixel electrode is electrically connected to a conductive layer beneath the pixel electrode in the downward direction, through a contact hole formed in an insulating film (refer to JPA-2006-317903).
The contact hole in this electro-optical device is large in horizontal size, and the electro-optical device decreases in display grade. For example, the contact hole in a liquid crystal device is so large in horizontal size that a pixel electrode has a large depression and elevation on the surface. This prevents an oriented film from being formed in a suitable manner. Furthermore, in a transmission-type liquid crystal device, an amount of display light decreases because light cannot pass through the contact hole. Furthermore, an area of the depression and elevation does not contribute to display, because the reflection direction of light is in disorder there, when the pixel electrode has the large depression and elevation on the surface in a reflection-type liquid crystal device.
On the other hand, a configuration is commonly employed that buries a plug in a contact hole in an inter-layer insulating film, and electrically connects the pixel electrode and an electrode beneath the pixel electrode (that is, in the downward direction), through this plug buried in the contact hole in the inter-layer insulating film (refer to JP-A-2011-64849). With this configuration, the contact hole is made smaller in horizontal size, thereby preventing the large depression and elevation from being formed on the surface of the pixel electrode.
However, in the conducting structure that uses the plug, it is necessary to additionally prepare a metal material, which is not in common use for the electro-optical device, such as tungsten, in order to form the plug. This increases the manufacturing cost. Furthermore, it is necessary to perform a step of sputtering metal to thicken a metal film for the plug and a step of smoothing an inter-layer insulating film by a chemical machinery polishing method, until the contact hole is filled. The sputtering step of these steps decreases productivity because it takes too much time to sputter metal to thicken the metal film for the plug.